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You are here:   OldClasses > 2012 > Alloeocomatella pectinifera | Shuting Jin

 

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Alloeocomatella pectinifera

(Clark 1911)

Red Feather Star

Shuting Jin (2012)

 

Fact Sheet

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Summary


Physical Description


Ecology


Local Distribution and Habitats


Commensalisms


Life History & Behaviour


Reproduction


Feeding


Cyclicity


Anatomy and Physiology


External Anatomy


Internal Anatomy


Physiology


Evolution & Systematics


Fossil Record


Phylogeny


Biogeographic Distribution


Conservation


Status


Threats


Resources


References


Acknowledgements


Contact

Physiology


​Locomotion

Feather stars can crawl as well as swim, using their water vascular systems and muscles to control the movements of their arms (Ruppert et al. 2004). When crawling, feather stars raise their body up over the substrate and "walk" with alternately movements of the downward-pointing arms (Ruppert et al. 2004). This type of movement was directly observed in the lab at Heron Island in all the specimens of A. pectinifera collected. When swimming, the body is held normally while the arms alternately move up and down (Ruppert et al. 2004).


​Circulation, Respiration, and Excretion

Circulation and respiration occurs via the water vascular system. Crinoids do not possess any specialized respiratory organs (Ruppert et al. 2004). Instead, gas exchange occurs at the surface of the tube feet (Ruppert et al. 2004). Crinoids have a full gut with a mouth, esophagus, intestine, rectum and anus. Excretion occurs from the anal opening, which is often at the top of a raised papilla that is thought to prevent waste from falling into the nearby oral opening (Lawrence 1987; Ruppert et al. 2004).

A specimen of A. pectinifera used for a preliminary feeding trial exhibited signs of stress when placed into a container just large enough to hold it in 400 mL of natural, room temperature seawater with 2 mL of concentrated algae (7 - 20 micron Thalassiosira weissflogii at 0.32 billion per mL) mixed into it. The specimen released a substance that tinted the water pink and held its arms and pinnules very stiffly in a partly curled position. The trial was terminated early out of concern for the animal. In contrast, animals kept in a larger 10 L container with circulation provided by a constant drip system and no added algae did not appear to release any colored substances and had relaxed, extended arms. The high algae concentrations and lack of circulation may have created hypoxic (low oxygen) conditions, resulting in respiratory stress in the animal. It was observed that A. pectinifera releases a reddish pigmented substance into the water when disturbed. It is unclear what function this serves, but if it is an alarm chemical or antipredator mechanism, then prolonged exposure to this chemical may be stressful to the animal.


Nervous System

The nervous system of feather stars occurs as three interconnected systems (Ruppert et al. 2004). The first system consists of an oral nerve ring with rays branching out into the arms and is mostly sensory (Ruppert et al. 2004). The second system is also sensory and consists of a nerve ring that branches into the arms and pinnules (Ruppert et al. 2004). The third system is responsible for motor action and is found centered on the calyx with rays branching into the arms (Ruppert et al. 2004).




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